1. Technical Field
The present invention relates to a system and method of controlling a fuel cell system, and more particularly, to a system and method of controlling a fuel cell system that simultaneously implements hydrogen purging and condensation water draining functions using a single valve.
2. Description of the Related Art
A fuel cell vehicle includes a fuel cell stack in which a plurality of fuel cells used as a power source are stacked, a fuel supplying system supplying hydrogen, which is a fuel, or the like, to the fuel cell stack, an air supplying system supplying oxygen, which is an oxidizing agent required for an electrochemical reaction, water and a heat managing system that controls the temperature of the fuel cell stack, and the like.
In particular, the fuel supplying system decreases pressure of compressed hydrogen in a hydrogen tank and supplies the compressed hydrogen of which the pressure is reduced to an anode of the fuel cell stack, and the air supplying system supplies external air sucked in by operating an air blower to a cathode of the fuel cell stack.
When hydrogen is supplied to the anode of the fuel cell stack and oxygen is supplied to the cathode of the fuel cell stack, hydrogen ions are separated through a catalytic reaction in the anode. The separated hydrogen ions are transferred to an oxidizing electrode, which is the cathode, through an electrolyte membrane, and the hydrogen ions separated in the anode generates an electrochemical reaction together with electrons and the oxygen in the oxidizing electrode, thus generating electrical energy may be obtained. In detail, electrochemical oxidization of the hydrogen occurs in the anode, and electrochemical reduction of the oxygen occurs in the cathode. Electricity and heat are generated due to movement of electrons generated through the above-mentioned process, and water vapor or water is generated by a chemical action that the hydrogen and the oxygen are bonded to each other.
In order to release hydrogen and oxygen that do not react and result in byproducts such as water vapor, water, and the heat generated in an electric energy generating process of the fuel cell stack, a draining device is provided. As such, gases, such as the water vapor, the hydrogen, the oxygen, and the like, are drained to the atmosphere through a draining path.
Meanwhile, an amount of water in the fuel cell stack should be appropriately adjusted. As an ion exchange membrane configuring a membrane electrode assembly is humidified, ion conductivity of the ion exchange membrane is increased, thereby making it possible to increase reaction efficiency of the fuel cell stack. On the other hand, when an amount of water is excessively large, a liquefaction process of the water vapor easily occurs to impede a contact between a catalyst and reaction gases, thereby making it possible to decrease reaction efficiency of the fuel cell stack.
In most fuel cell systems, a hydrogen vent valve for adjusting the amount of hydrogen that is drained from the system and for adjusting an amount of water in a fuel cell stack is utilized to increase fuel efficiency. while still preventing a surplus In these systems, a hydrogen vent valve is repeatedly opened and closed by a control signal to allow a fuel and condensate water in the fuel cell stack to remain in the system for a predetermined time and be drained to the outside after the predetermined time has expired.
However, the point in time at which the condensate water needs to be drained and a point in time at which the fuel needs to be drained may be different from each other. As such, there is increased degree of likelihood that a flooding phenomenon will occur in the fuel cell stack, the hydrogen will be excessively drained, thereby decreasing fuel efficiency, and the durability of the stack may be decreased due to a decrease in a concentration of internal reaction gas.